Ellipsoid Body and Medulla Defects and Locomotion Disturbances in sbr (small bristles) Mutants of Drosophila melanogaster

The sbr gene is an ortholog of evolutionarily conservative nxf1 (nuclear export factor) genes that control nuclear-cytoplasmic transport of mRNA in various eukaryotic organisms. Mutations of sbr exhibit a broad range of pleiotropic effects, which are characteristic of “housekeeping” genes. Certain allele-specific manifestations of the sbr gene in neurogenesis and behavior facilitate a deeper understanding of not only universal but also highly specialized functions of this gene. Among such characteristic features of adult males with an sbr¹² mutation are reduced locomotor activity as revealed in the negative geotaxis test and significant morphological disruptions of the ellipsoid body and the medulla, both of which are important for locomotion. The character of defects in the ellipsoid body and the medulla suggests that the SBR protein is essential for the normal formation and functioning of these nerve centers, and that the protein carries not only universal but also specialized functions.